Si- and C-rich structure of the 6H-SiC(0001) surface

The reconstructions of the 6H-SiC(0001) surface under both Si-rich and C-rich conditions were studied using field ion-scanning tunneling microscopy (FI-STM). The sample was cleaned by in situ Si beam etching at 900-1000°C. The as-cleaned surface showed a (√3×√3) structure. The Si-rich phases were produced by annealing the sample in a Si flux. With increasing Si concentration, (2×2), (2√3×6√3), (3×3), and (7×7) reconstructions were observed. Reaction of the Si-rich phases with C₂H₂ molecules at 1050 °C resulted in the formation of a C-rich surface, which exhibited a (2×2)/(6×6) reconstruction. A structure model for (√3×√3) reconstruction is proposed, and possible applications of using the surface reconstruction to selectively grow SiC polytype is discussed.